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The thermal conductivity of Cis and Trans Decahydronaphthalene Schoening, M. A.

Abstract

A convenient method for measuring the thermal conductivity of liquids is that introduced by Bridgman in 1923. In this procedure the liquid is held in the annular space between two concentric cylinders. By supplying heat at & definitely known rate to the inner cylinder and measuring the temperature drop across the liquid, the thermal conductivity of the liquid may be determined. Because the liquid film is only 0.04 cms. in thickness and the temperature drop across the film does not exceed one degree, convection withing the liquid is prevented. The temperature drop across the film is measured by means of differential thermocouple Bridgman's cell has the advantage over other thermal conductivity apparatuses In that it requires only a very small volume of liquid for the measurement. In this investigation the thermal conductivities of cis- and trans-decahydronaphthalene were measured. When the results were compared with those of Levelton and Perris, who determined the same quantities by the method of Bates, it was found that lower values had been obtained for both the thermal conductivities and the temperature coefficients. The difference in the conductivity may be explained in part by the surface film discovered by Bates. In Bridgman's apparatus no allowance is made for this film and the measured temperature drop represents the average temperature gradient from one boundary of the liquid to the other. Unless this surface film changes considerably with temperature it would offer no explanation for the very definite difference found in the temperature coefficients. Attempts to explain the divergence of results on the basis of purity of materials meet with little success because of a lack of necessary data. An attempt has been made to design a simplified cell based on the same principles as Bridgman's cell and is offered herewith.

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